William Shakespeare, who celebrates his 450th birthday this year, toked on Mary Jane Green.

South African scientists have discovered that 400-year-old tobacco pipes excavated from the garden of William Shakespeare contained cannabis, suggesting the playwright might have written some of his famous works while high.

Residue from early 17th century clay pipes found in the playwright’s garden, and elsewhere in Stratford-Upon-Avon, were analyzed in Pretoria using a sophisticated technique called gas chromatography mass spectrometry, the Independent reports.

Of the 24 fragments of pipe loaned from the Shakespeare Birthplace Trust to University of the Witwatersrand, cannabis was found in eight samples, four of which came from Shakespeare’s property.

There was also evidence of cocaine in two pipes, but neither of them hailed from the playwright’s garden.

Shakespeare’s sonnets suggest he was familiar with the effects of both drugs.

In Sonnet 76, he writes about “invention in a noted weed”, which could be interpreted to mean that Shakespeare was willing to use “weed”, or cannabis, while he was writing.

In the same sonnet it appears that he would prefer not to be associated with “compounds strange”, which can be interpreted, at least potentially, to mean “strange drugs” (possibly cocaine).